1. Field of the Invention
The present invention relates to an electric motor vehicle in which wheels are driven by an electric motor, and more particularly to a collision-preventing apparatus for an electric motor vehicle which in a case where an obstacle is present in front of the electric motor vehicle, prevents a collision of the electric motor vehicle against the obstacle.
2. Description of the Related Art
In recent years, development has been made in the field of electric motor vehicles using an electric motor as a driving source in view of such needs as improvement of the environment, an extrication from dependence on fossil fuels, and a diversification of energy sources. As such electric motor vehicles, for instance, forklifts, golf carts, and various other vehicles are known.
In braking such an electric motor vehicle, unlike an ordinary vehicle using an internal combustion engine as a driving source, it is possible to apply brakes by means of electric braking. With this electric braking, however, it is impossible to bring the vehicle to a standstill completely or suddenly. Accordingly, frictional braking by means of hydraulic pressure and electric braking are used jointly in many cases.
Meanwhile, when an obstacle is present in front of the vehicle, the driver generally operates a foot brake to decelerate the vehicle or bring the same to a standstill, or steer the vehicle by maneuvering a steering wheel, so as to prevent the vehicle from colliding against the obstacle. However, should the driver fail to notice such an obstacle, or if the obstacle is a vehicle running just in front of it, there are cases where the driver fails to visually measure the relative speed or the following distance with respect to that vehicle. As a result, the vehicle can collide against that obstacle.
To cope with such a problem, apparatus in which the foot brake is actuated by detecting an obstacle by means of a radar apparatus have hitherto been proposed in Japanese Patent Application Laid-Open Nos. 63-32388 and 64-4611. According to the apparatus disclosed in these publications, it is possible to prevent a collision of an automobile against an obstacle.
However, with the apparatus disclosed in Japanese Patent Application Laid-Open No. 63-32388, an actuator capable of producing a large force is required so as to actuate the brakes automatically. For this reason, the apparatus becomes not only large in size but expensive.
In addition, with the apparatus disclosed in Japanese Patent Application Laid-Open No. 64-4611, since the apparatus is used for autonomous running, a control unit for controlling the braking force is bound to become complicated.